The purpose of the septic tank is to separate the solids from the liquids in the wastewater stream and to begin the process of breaking down contaminants. The septic tank can be constructed of concrete, steel, fiberglass or polyethylene and can range in size from about 2300 litres to 5000 litres. To give you an idea of how large this is, consider that up to 200 litres of water fit in a standard bathtub and ordinary toilets use up to 20 litres per flush. The septic tank typically has two chambers. The wastewater from your house, called “influent”, enters the first chamber and its velocity slows so that the heavier solids can settle out of the chamber, and the lighter materials can float to the surface. The accumulation of settled solids at the bottom of the tank is called “sludge” and the lighter solids (greases and fats) which form a mass on the surface of the liquid in the septic tank is called “scum”. In between the sludge and the scum is liquid waste. Microorganisms, like bacteria, and other natural processes act to decompose the waste materials in the liquid waste. Sludge and scum are also digested and compacted into a smaller volume. This is the first step in the process of purifying your household wastewater. When the first chamber of the tank becomes filled, the liquid waste begins to fill the second chamber. The chambers of the septic tank are designed to prevent the movement of sludge and scum to the second chamber, allowing only the movement of liquid. Once the second chamber is filled, as more influent enters the first chamber, an equal amount of partly treated liquid flows into the second chamber, while an equal amount flows out into the leaching bed. The water flowing out into the leaching bed is called “effluent”. The purpose of the leaching bed is to further treat the wastewater. A grid work of perforated pipes or clay tiles in the leaching bed area evenly distributes the effluent over natural soil or imported fill. Sometimes a distribution tank is used at the head of the pipes to more evenly distribute the effluent to the pipes. The perforations in the pipe allow the effluent to escape to the soil. As the effluent filters through the soil, microorganisms in the soil digest and remove the remaining impurities (such as suspended solids and/or bacteria). Eventually, the purified water reaches the groundwater. As you can see, the operation of your septic system is fairly automatic and can work quite well by itself with very little maintenance required by the homeowner. Note the key words though, “little maintenance”, not “no maintenance”.
Over time, the sludge will build up at the bottom of the tank. The rate of the buildup will depend on the size of your tank (bigger is better), the volume of wastewater entering the tank, and the volume of solids in the wastewater stream. If the sludge is allowed to accumulate to the height of the outlet pipe, it could flow into the next chamber and then out into the tile bed. The pipes in the tile bed can become rapidly clogged by sludge. When the pipe is all blocked and the wastewater can no longer leach into the soil, it will seep to the surface of the ground, or worse yet, backup into your house. Not only can a clogged septic system be hazardous to the environment and to your family’s health, it also represents a very expensive repair bill. Once the pipes become clogged, there is no quick fix; the entire system must be dug up and replaced.
To prevent the clogging of the system, every two to three years (depending on the tank size and use of the system), a licensed sewage disposal contractor should be hired to pump out the tank to remove the buildup of sludge. Pumping should be more frequent for a smaller tank, where more people are living in the house and for houses with garbage disposals. Not only will this increase the capacity of the system by creating more room for the wastewater, but it will also prevent the sludge from entering the tile bed area.
The access lids at either end of the tank, where the baffles are located, must be uncovered. The serviceman will remove them at the time of the pump out. Never inspect or pump out a septic tank yourself. There is no oxygen in the tank for you to breathe and the tank contains deadly methane gas (produced by the decomposition of organic matter in the tank), which can kill you in only a few seconds – that’s one of the reasons why the tanks are kept sealed.
Because septic systems rely on microscopic organisms to break down the waste material, it is important that you don’t “poison” these organisms. Even small amounts of paints, solvents, thinners, nail polish remover and other common household compounds flushed down the drain can kill the organisms that break down organic material. Laundry bleaches; toilet bowl cleaners and caustic drain openers can slow the treatment process, allowing the sewage to pass through to the leaching bed without proper treatment. However, moderate use of these materials should not interfere with the operation of the septic system. You should avoid putting anything into the septic system that doesn’t breakdown naturally or anything that takes a long time to break down. Materials such as oils, grease, and fat, disposable diapers, tampons and their holders, condoms, paper towels, facial tissues, cat box litter, plastics, cigarette filters. Coffee grounds, eggshells, and other kitchen wastes, should never be put into the septic system. You should also avoid the use of in-sink garbage disposal units (“Garburators”).
Reduce the use of phosphate-based detergents, soaps and cleaners. The phosphorus in detergents doesn’t break down in a septic system. When the phosphorus leaches into nearby bodies of water, it can promote algae growth and can impair water quality and fish habitat.
Every time you put water into your septic tank, that same amount of water moves into the leaching bed. So the faster you put the water into the tank, the faster it moves into the leaching bed. However, it takes time for the solids to settle out of the liquid waste and for the microorganisms to digest the solids. The longer the “retention time”, the more purification that occurs. The “retention time” is the time that the wastewater is allowed to remain in the septic tank. If you cause the water to move too quickly through the system, less purification occurs before the water reaches the leaching bed and the effluent may be discharged to the soil while still containing dangerous pollutants in unacceptable concentrations.
Whenever possible, you should try to regulate the amount of water entering the septic system. Space loads of laundry throughout the week instead of all at once. Reduce water usage by installing water saving features in plumbing fixtures and by only running the washer or dishwasher when full. Try taking shorter showers rather than full baths. Repair leaky faucets, which can waste about 10,000 litres of water a year. A silently leaking toilet can waste up to 20 times that amount. Ensure that foundation drainage, surface water from roofs, yards, garage floors and other sources of oily wastes, furnace condensate, and water softener backwash is excluded from the septic tank and the disposal field.
Looking after the leaching bed is easy. There’s nothing you have to do, but there are a few things you shouldn’t do. The area over the leaching bed should have a good cover of grass. Good ventilation and adequate sunlight should also be maintained to promote evaporation. You should avoid constructing patios, decks, parking areas in the area of, or over, the leaching bed. The weight of which could crush pipes. You should not drive recreational vehicles or machinery over the bed, as the weight could crush the pipe or compact the soil covering the bed; this includes no skating on top of rinks, gardens and tile beds. Covering the leaching bed could also prevent oxygen from getting into the soil. The microorganisms responsible for digesting the waste material need oxygen to survive and function. Do not plant trees or shrubs near the leaching bed. The roots can travel significant distances and can plug and damage the tile. Don’t water the grass over the tile bed. The additional water may interfere with the ability of the soil to absorb liquids and break down waste.
Sewage waste may be spread on suitable approved farmers fields. If the fields are wet or frozen, the waste must be taken to an approved lagoon or sewage treatment plant. Within the next several years, the Nutrient Management Act will put a stop to field spreading of untreated sewage waste on farmer’s fields.
What you smell is methane gas, which is produced when organic materials decompose.
Some signs that the septic tank needs to be pumped out, that there may be a blockage, or that there may be a problem with the tile bed are:
Slow toilets or other fixtures
Odors coming from plumbing pipes
Water coming up in sinks, tubs or showers after flushing the toilet or doing a load of laundry
Seepage in the vicinity of the septic system
Green stripes or patchy lawn over tile bed
Wooden boxes can be built to fit larger than the lids and brought up to 1-½ inches from the surface of the ground. This allows for a patio slab to cover the opening, also allowing a lawn mower to pass over it unrestricted. Concrete culverts can also be used with their own lids.